Heat stabilizer for vinyl compounds



Patented May 25, 1943 HEAT STABILIZER FOR VINYL COMPOUNDS Winfield Scott, Akron, Ohio, assignor to Wingfoot Corporation, Wilmington, Del., a corporation of Delaware No Drawing. Original application April 1, 1941,

Serial No. 386,316. Divided and this application March 26, 1942, Serial No. 436,319

Claims.

This invention relates to a method of improving the stability of polymeric masses and articles made therefrom against the effect of heat.

Polymers of various types, while substantially clear when freshly made, often undergo discoloration and deterioration from heat, such as that employed in molding and processing these polymeric masses to form useful articles. Various substances have been added to the polymers to retard or prevent such discoloration and darkening but not always with fully satisfactory effects.

It has now been found that masses resulting from the polymerization of monomers which inelude or comprise vinyl chloride may be heatstabilized by the addition to the mass after polymerization of a small amount of a metal amide. This is especially true of the sulfonamides of the alkali metals, alkaline earth metals and lead, the term "sulfonainide being employed to cover this class including benzine, toluene and naphthalene sulfonamides and the like. Preferably, there is employed one of the following: sodium benzene sulfonamide, sodium p-toluene sulfonamide, barium ptoiuene sulfonamide, barium naphthalene suifonamide, magnesium p-toluene sulfonamide, magnesium benzene sulfonamide, lead benzene sulfonamide, lead p-toluene sulfonamide, and lead naphthalene sulfonamide. Barium p-toluene sulfonamide is particularly effective. The compounds of any of the foregoing metals and benzene sulfonamide and naphthyl sulfonamide may also be used.

In order to test the stabilizing effect of the foregoing compounds, they were incorporated in a formula consisting of 100 parts of a copolymer of 85% vinyl chloride and vinylidene chloride, 40 parts of tricresyl phosphate, and 3 parts of one of the foregoing heat stabilizers. The eopolymer, the plasticizer and the stabilizer were intimately mixed and then placed on a hot rubber mill. After mixing until uniform, the prod not was sheeted off the mill.

Test sheets were then made by heating samples of the formula in a mold to produce a block 4" square and u in thickness. The effectiveness of the heat stabilizer was observed by noting the amount of discoloration produced or by comparison with a control containing no thermal stabilizer. The samples were heated at a temperature of 305 F. for a period of 30 minutes, the control under these conditions becoming black and opaque. On the other hand, the samples containing approximately 3% of stabilizer on the copolymer retained their transparency and darkened very little.

While the invention has been described particularly with reference to vinyl chloride-vinylidene chloride copolymers, it may also be used with other copolymers containing vinyl chloride. Thus, copolymers of vinyl chloride and one of the following: butadiene, acrylonitrile, methacrylonitrile, styrene, vinyl bromide; isoprene, vinyl esters of carboxylic acids, such as vinyl acetate.

esters of acrylic and substituted acrylic acids, such as methyl and ethyl acrylates and methacrylates, may also be heat stabilized by the incorporation of one of the substances herein set forth or other substances of the same class, i. e., amides and imides, particularly phthalimides and sulfonamides, of the alkali metal and alkaline earth metal groups and lead.

This application is a division of my application Serial No. 386,316, filed April 1, 1941.

I claim:

1. A method. of heat-stabilizing polymerized masses containing a polymer of vinyl chloride which comprises adding to the polymer one of the group consisting of the alkali metal, the alkaline earth metal, and the lead aryl sulfonamides.

2. A method of heat-stabilizing masses resulting from the polymerization of monomers, one of which is vinyl chloride, which is characterized by adding to the polymer one of the group consisting of the alkali metal, the alkaline earth metal and the lead aryl sulfonamides.

3. A method of heat-stabilizing copolymers of vinyl chloride and vinylidene chloride which comprises adding to the copolymer one of the group consisting of the alkali metal, the alkaline earth metal and the lead aryl sulionamides. 4. A method of heat-stabilizing masses resulting from the polymerization of monomers one of which is vinyl chloride, which is characterized by adding to the polymer an alkali metal aryl sulfonamide.

5. A method of heat-stabilizing masses resulting from the polymerization of monomers one of which is vinyl chloride, which is characterized by adding to the polymer sodium aryl sulfonamide.

WINFIELD SCOTT. 

